All types of gate-controlled semiconductor devices having an insulated gate are included, such as for example IGBTs, MOSFETs, vertical MISFETs and MIS-gated thyristors.
Such devices are particularly used in applications in which it is possible to benefit by the superior properties of SiC in comparison with especially Si, namely the capability of SiC to function well under extreme conditions. SiC has a high thermal stability due to a large band gap between the valence band and the conduction band, so that it will have a stable function at much higher temperatures than Si, namely well up to 1000K. Furthermore, it has a high thermal conductivity, so that SiC devices may be arranged at a high density. SiC also has a more than 5 times higher breakdown field than Si, so that it is well suitable as material in high power devices operating under conditions where high voltages may occur in the reverse direction of the device.
There are over 250 polytypes of SiC, and the most important ones are 3C, 4H, 6H and 15R, since good species thereof may be produced without any complications. The CVD-technique may preferably be used for the production of such SiC crystals. SiO.sub.2 has until now primarily been used as a material for the insulating layer of semiconductor devices of the type defined above. However, the conductivity of the channel created at the interface in such devices is not as high as desired, so that the on-slate-current capability of such devices is limited. This is due to the comparatively high trapping density at the interface between the SiC and SiO.sub.2 layers. Accordingly, the charge carriers (electrons or positive holes) are scattered at the interface as a result of these traps. An increase of the gate voltage increases the carrier density in the conducting channel, but this advantage is counteracted by the resulting limited carrier mobility. Furthermore, increasing the gate voltage above a certain limit will besides an extensive scattering of the carriers at the interface procure tunnelling of the carriers into the dielectric reducing the current in the channel. SiO.sub.2 has thereto a breakdown field not adapted to the conditions under which SiC itself may function well.